1. Field of the Invention
The present invention relates to a reproducing apparatus, a recording/reproducing apparatus and a reproducing method for an optical recording medium.
2. Description of the Related Art
In holographic recording, two-dimensional digital data is multiplexedly recorded by using two light beams of a reference beam and an object beam, thereby performing three-dimensional recording. As an example of the multiplex-recording, there is an angle multiplexing method. In the angle multiplexing method, a plurality of pieces of two-dimensional information are multiplexed and recorded on the same position by varying the angle of irradiation of the reference beam (see, for example, JP-A 2004-4434).
In the case of reproducing data recorded in such a manner from a medium, the medium is irradiated with the reference beam at the same angle as that upon recording. The reference beam is diffracted by the recording medium and a reproduction beam is obtained. The reproduction beam is received by a two-dimensional image pickup device such as a CCD or a CMOS sensor. A resultant output is processed, thereby obtaining two-dimensional digital data recorded on the medium.
In the angle multiplexing method, however, the pattern of the reproduction beam is extremely sensitive to the irradiation angle of the reference beam at the time of reproduction. If the irradiation angle of the reference beam shifts even slightly, a desired reference beam pattern cannot be obtained. In the conventional method, the whole page of information is first read out, a page address is extracted from the read page, and whether the read page is a desired page or not is determined by using the extracted page address. In this method, however, when the read page is not a desired page, the whole page has to be read again, and it takes time for data reproduction. In addition, even in the case of reading a small amount of data in a page, the whole page has to be read out and it takes time to transfer the data.